| Heavy metals pollution is a worldwide problem in the environment and ecological system.Due to unreasonable emission of the "three wastes" from industrial production and using all kinds of pesticide and fertilizer in modern agriculture,the content of heavy metals in soil is seriously the pollution.Especially,the research of the heavy metals cadmium,mercury,lead enrichment in organism body and antibiosis has attracted more and more attention at the present.The influence of heavy metal pollutions on growth of Korean larch(Larix olgensis)and insect-resistance was studied by indoor experiment and outdoor control stress experiment combined sampling survey method in this paper.Effect of different concentrations of Cd?Hg and Pb pollution stress on the growth of Korean larch was compared between the treatments in outdoor pot experiments,enrichment of heavy metal in Korean larch needles was also ananlyzed,and defense related substances of secondary metabolites tannins,phenolic acid activity of protective enzymes POD or SOD were changed with prolonging stresss time.Experiment of different heavy metal pollution treatments on growth and development of gypsy moth(Lymantria dispar)was conducted to measure activity changes of detoxifying enzymes in larvae in the Insect Chemical Ecology Laboratory of Northeast Forestry University.Each heavy metal was set with 3 concentrations as Cd(Low 1,Middle 2,High 4mg· kg-1),Hg(Low 1.5,Middle 3,High 6mg· kg-1),Pb(Low 500,Middle 1000,High 1500mg· kg-1).The results were as follows.1?There was a significant effect on the growth of Korean larch in the high concentration treatments of heavy metal stress-pollution.There was no obvious inhibition effect on the plant height,root length and plant diameter above ground in the treatment of Cd(low,middle,high),Hg(low,middle,high)and Pb(low,middle),but the treatment of Pb(high)on the plant height,root length and plant diameter above ground exhibited a significant inhibition.However,biomass accumulation was significantly reduced in the Pb(middle,high)treatment.There was no significant effect on the biomass distribution ratio of aboveground and underground parts of Korean larch in the heavy metal pollution treatments.2?Enrichment of heavy metal in in the larch needles presented a dependent relationship with concentration and time.There were significant differences for enrichment in the needles between the treatments of Cd,Hg,Pb different concentrations(P<0.05),and the enrichment presented a positive correlation with the time and the concentration of the treatment in 30 days.The enrichment contents were significantly increased with the increase in the dose and duration of treatment(P<0.05).Heavy metal content in the needles after the 60 days treatment were significantly decreased in comparision with the 30 days treatment(P<0.05),which indirectly confirmed that Korean larch for CD,Hg and Pb pollution stress has a certain tolerance and detoxification capacity.3?There was a significant interfering effect on the activity of main defense proteins POD,SOD,PPO,PAL,CI and TI in the larch needles from the heavy metal pollutions.POD activity showed decreased firstly and then increased,SOD activity showed the trend of first increased and then decreased with the concentration increased and treatment time prolonged in the CD(low.middle,high)and Hg(low,middle,high)treatments of 30 to 60 days after the treatments;activity of POD and SOD was continued to decline in the Pb(low,middle,high)treatments;the activity of PAL.PPO.PAL,Cl and TI was increased with increasing CD.Hg and Pb concentrations and prolonging stress time.4?Tannin,phenolic acid content in the needles of larch seedling had a significant response for Cd,Hg and Pb stress.The tannin content in the CD(low,middle,high),Hg(low.middle,high)treatments was increased firstly and then decreased with increase of concentration in 30 to 60 days after the treatments,but it was significantly decreased in the Pb(low.middle,high)treatments.After 60 days treatment.Tannin content in the CD(low),Hg(low and high),Pb(low and high)treatments was significantly higher than that in the treatments of 30 days,but the tannin content in the CD(high),Hg(middle),Pb(middle)treatments was significantly lower than that of the treatments after 30 days.Total content of phenolic acid in the CD(low,middle,high)and Pb(low,middle,high)treatments was firstly increased and then decreased with increasing concentration,but it was increased first and then decreased with the treatment concentration in the Hg(low,middle,high)treatments.5?There was a significant influence on the detoxification enzyme activity,larvae growth and development of gypsy moth in the heavy metal pollution treatments.After the larvae feeding on CD(low,middle,high),Hg(low,middle,high),Pb(low,middle,high)treatmenting needles,the average weight of 3rd and 4th instar larvae,the larvae pupate rate,pupal weight and adult emergence rate were significantly decreased(P<0.05).The activity of both protective enzymes of SOD,POD and detoxification enzymes of ACP,AKP and GSTs had different degrees of inhibition.The experimental results confirmed that Korean larch has a super-accumulation ability for maintaining growth and biological repair in heavy metal contaminated soil.The research of the antioxidant defense system induced by heavy metals was short of the time,and it is hard to be applied in the complex ecological environment of nature.Therefore,how to combine the indoor control with the field reality for scientifically respond to the poison mechanism of the antioxidant enzyme to the insect,was needed to be further studied.The above experimental results,may provide a good theoretical basis for further research on eco-physiological response mechanism of forest pest and for the forest ecosystem health and integrated pest management. |
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